(1) Field of the Invention
This invention relates to storage batteries and, more particularly, to a method and apparatus for determining the maintenance and charge conditions of a lead storage battery.
(2) Prior Art
Known test techniques of testing lead acid batteries include a determination of physical properties of the individual cells, such as cell voltage or specific gravity. Such techniques have been greatly restricted in their usefulness by the advent of through the cell wall connectors and the maintenance free batteries. Accordingly, it would be desirable to have a battery tester based purely on electrical measurements at the battery post. Further, an electrical measurement, in contrast to a measurement with a hydrometer, can be readily incorporated into a computer diagnostic analysis which is often performed in the course of vehicle maintenance.
Prior art attempts to provide such electrical measurement devices and methods have not provided the required combination of accuracy, simplicity, ruggedness and low cost. In particular, prior art attempts have often been characterized by an inability to test batteries regardless of battery state of charge, battery temperature and battery capacity, and an inability to interface with a microprocessor based automatic test system. These are some of the problems this invention overcomes.